After reading several positive posts around here, I replaced my venerable iPod G5 Video with a little Sansa Clip+ and a 16GB flash card. Missing AAC support was a deal breaker, but Rockbox was reported to run fine.

I must say, compared to the absolutely flawless experience with my last iPod, I'm quite dissatisfied. It started with a bug of Rockbox 3.7.1 that large SD cards are sometimes not initialized properly (and thus don't appear in the menu), which affected my Transcend model. An upgrade to the latest daily build fixed this.

An issue, that I can't fix with whatever build, is annoying CPU noise. At the beginning of tracks and during rebuffering of longer tracks there is a short humming sound (like a bumblebee) mixed with a fast sequence of random high frequency tones. The sound differs as a function of data format and content. It is very homogeneous with WAV tracks (only humming) and different with lossy and lossless codecs. The same file encoded with FLAC and AAC leads to different short distortions. It is only audible for tracks with initial silence or very dynamic content, for example classical music with quiet passages or audio books. The original firmware does not show this behavior. It is probably a throttling issue. Rockbox just reads and decodes the file in a regular loop as fast as the CPU can deliver it. Due to cheap hardware design this leads to audible inference on the output. The original firmware probably works around this by some form of flow control and doesn't read the data any faster than required. But, as I've said, due to missing AAC support the original firmware is not an option.

The phenomenon is only audible with my headphones. The Creative EP-630 have a rather large sensitivity of 106 dB. I tried to record the distortion over a line-input and it is non-existent there. That made me think about the common practice of shutting people up with RMAA results or telling them that what they hear must be placebo. High-impedance, line-level inputs do not necessarily capture the same as what a sensitive headphone outputs.

Can anyone, who also owns sensitive earphones, recommend a comparable player (no video, real buttons) with flawless output? It would be nice if I could re-use the SD-card.

I am completely unable to reproduce any noise at all on the Clip+ using EP-630s, in a quiet room, and my "silence.wav" that I used when trying to figure out where the noise on the Clipv2 comes from. I also tried normal music with the gain digitally adjusted down 30 dB. If its really so obvious for some people using these exact headphones and real music, then I suspect my player is somehow different. Sandisk has released different hardware revisions where they change minor things, and my player is the oldest revision. I'm guessing people who hear noise have bought their players more recently (IIRC the last revision showed up in July or so). Maybe they've changed something else.

I'm guessing people who hear noise have bought their players more recently (IIRC the last revision showed up in July or so). Maybe they've changed something else.

I purchased my Clip+ in May 2010 from amazon. I assume amazon cycles through old/new stock pretty quickly, so it was probably manufactured not long before May. Mine has those noises as well, but not to the degree googlebot is talking about. My IEMs are slightly more sensitive (107 db/mw) than the EP-630.